The prior art discloses intraocular lenses. See for example U.S. Pat. No. 6,536,899 to Fiala; U.S. Pat. No. 6,557,998 to Portney; U.S. Pat. No. 6,814,439 to Portney; U.S. Pat. No. 7,073,906 to Portney; and U.S. Pat. No. 7,093,938 to Morris. U.S. Pat. No. 7,073,906 is directed to an “Aspherical Diffractive Ophthalmic Lens.” U.S. Pat. No. 7,093,938 is directed to a “Bifocal Multiorder Diffractive Lenses for Vision Correction.”
IOL means Intraocular Lens. D means Diopters. The refractive index of air is 1.000 and of an average human cornea is about 1.376. The optical power of the human cornea is generally about 40 D; of the human lens (relaxed) is generally about 20 D; of an entire human eye is generally about 60 D; and the maximum change in the power of the human eye due to accommodation is generally about 8 D in a young human eye.
The values for peak wavelength sensitivity of the human eye under scotopic conditions is 507 nanometers (nm), and under photopic conditions is 555 nm.
Photopic vision means day time vision. Mesopic vision means evening vision. Iris means the contractile membrane perforated by the pupil, and forming the colored portion of the eye.
As used herein, the term “near vision” means vision produced by an eye that allows a subject to focus on objects that are within a range of about 25 cm to about 40 cm from the subject, or at a distance at which the subject would generally place printed material for the purpose of reading. As used herein, the term “intermediate vision” means vision produced by an eye that allows a subject to focus on objects that are located from about 40 cm to about 2 meters from the subject. As used herein, the terms “far vision” or “distant vision” means vision produced by an eye that allows a subject to focus on objects that are at a distance that is greater than 2 meters, at a distance of 5 meters or about 5 meters from the subject, or at a distance of 6 meters or about 6 meters from the subject. For example, an add power of 1 Diopter is suitable for focusing an object onto the retina that is located at a distance of 1 meter from an emmetropic eye in a disaccommodative state (e.g., with a relaxed ciliary muscle), while add powers of 0.5 Diopter, 2 Diopters, 3 Diopters, and 4 Diopters are suitable for focusing an object onto the retina that is located at a distance of 2 meters, 50 cm, 33 cm, and 25 cm, respectively, from an emmetropic eye in a disaccommodative state. As used herein “far focus”, “near focus”, and “intermediate focus” means a focus produce at the retina or image plane of a subject eye or a model eye that corresponds to far vision, near vision, and intermediate vision, respectively.
A multifocal optic or lens may be characterized by “base power” and at least one “add power”. As used herein the term “base power” means a power (in Diopters) of an optic, or portion thereof, required to provide distant vision or a far focus at the retina of a subject eye when the optic or lens is disposed in the eye. As used herein, the term “add power” means a difference in optical power (in Diopters) between a second power of the optic or lens and the base power. When the add power is positive, the sum of the add power and the base power corresponds to a total optical power suitable for imaging an object at some finite distance from the eye onto the retina. A typical maximum add power for an optic or lens is about 3 Diopter or about 4 Diopters in the plane of the lens, although this number may be as high as 6 or more Diopters (an intraocular lens add power of 4.0 Diopters is approximately equal to an increase in optical power of about 3.2 Diopters in a spectacle lens).
Refraction herein means the change of direction of propagation of light either at a continuous interface between dielectric media having distinct indices of refraction, or bending of light due to a gradient in an index of refraction in the media through which the light propagates.
The pupil of the human eye is generally smaller in photopic than in mesopic (or scotopic) conditions. The majority of middle age people have a pupil that, during day time, is within 1.1 millimeters (mm) of 3.4 mm in diameter, and during evening time is within 1.1 mm of 4.3 mm diameter. During night time, pupil size of middle aged people may range to larger than 5 mm. Pupil size decreases with age. Young people may have a pupil size that is as large as 9 mm.